Production of low density products by additive manufacturing

Abstract

Provided herein according to some embodiments is polymerizable liquid useful for the production of a three-dimensional object by additive manufacturing, said polymerizable liquid comprising a mixture of: (a) at least one photopolymerizable component; (b) a photoinitiator, (c) at least one heat polymerizable component; and (d) heat expandable microspheres. A method of making a three-dimensional object from such a polymerizable liquid by additive manufacturing and objects so produced are also provided.

We claim: 
     
         1 . A method of making a three-dimensional object, comprising:
 (a) producing an intermediate object from a dual cure resin by additive manufacturing, wherein the dual cure resin comprises heat expandable microspheres;   (b) optionally cleaning said intermediate object; and then   (c) further curing said intermediate object by contacting the intermediate object with water and heating and/or microwave irradiating said intermediate object for a time and at a temperature sufficient to expand said microspheres.   
     
     
         2 . The method of  claim 1 , wherein said additive manufacturing comprises a bottom-up stereolithography manufacturing method. 
     
     
         3 . The method of  claim 1 , wherein said intermediate object comprises a polymer scaffold produced by the photopolymerization of a photopolymerizable component in the dual cure resin; and wherein said polymer scaffold degrades when the intermediate object is heated. 
     
     
         4 . The method of  claim 1 , wherein said three-dimensional object is rigid, flexible, or elastic. 
     
     
         5 . The method of  claim 1 , wherein said three-dimensional object is comprised of polyurethane, silicone, or epoxy. 
     
     
         6 . The method of  claim 1 , wherein said intermediate object comprises a polymer scaffold produced by the photopolymerization of a photopolymerizable component; and wherein said polymer scaffold softens during said heating and/or microwave irradiating. 
     
     
         7 . The method of  claim 1 , wherein said microspheres comprise a hollow thermally expandable shell and a propellant contained in said shell. 
     
     
         8 . The method of  claim 7 , wherein said shell comprises a thermoplastic polymer shell. 
     
     
         9 . The method of  claim 7 , wherein said shell comprises polyacrylonitrile, polyvinyl dichloride (PVDC), polyvinyl chloride (PVC), polyamide or polyacrylate. 
     
     
         10 . The method of  claim 7 , wherein the propellant is a low-boiling point liquid. 
     
     
         11 . The method of  claim 7 , wherein the propellant is a liquified gas. 
     
     
         12 . The method of  claim 11 , wherein the liquified gas comprises isobutane or isopentane. 
     
     
         13 . The method of  claim 1 , wherein the dual cure resin is a flexible polyurethane resin. 
     
     
         14 . The method of  claim 1 , wherein said additive manufacturing comprises continuous liquid interface production. 
     
     
         15 . The method of  claim 1 , wherein said heat expandable microspheres are present in an amount of from 1 percent by weight to 10 percent by weight. 
     
     
         16 . The method of  claim 1 , wherein the volume of said intermediate object is increased by at least 5 percent by said heating and/or microwave irradiating step. 
     
     
         17 . The method of  claim 1 , wherein said three-dimensional object comprises a regular or irregular open-cell lattice. 
     
     
         18 . The method of  claim 1 , wherein said three-dimensional object comprises a cushion, shock absorber, thermal insulator, or electric insulator.